368 
BULLETIN OF THE BUREAU OF FISHERIES, 
There was a striking difference in the velocities of current in Lake Keokuk in 
July and September. In July there was a drop in the rate of current from 1.4 
foot per second at Burlington to 0.3 at Dallas. In September the river was rising 
and the difference between the two points became very slight, the figures being 2.2 
at Burlington and 2.18 at Dallas. Near the dam, where the current in July was very 
slow, in September its velocity reached 1 foot per second. 
It would be very interesting to know how the rise of the river affects the body 
of water in Lake Pepin, but unfortunately information for this comparison is lack- 
ing. Even the fluctuations of the water level in this lake are unkown, because 
there have been no stage observations made, the nearest stations being the regular 
gauges at Red Wing, above the lake, and at Reads Landing, below the mouth of 
the Chippewa River. 
The velocity of the current is less near the shore and greater in the main 
channel. Many dikes built to improve navigation and to keep the water running 
faster in a narrow channel have great influence on the currents, the water between 
the dikes being often almost stagnant, especially when the dikes are located at 
very close intervals. The current in the sloughs is usually slower than in the main 
channel, whereas many of the tributaries are very swift streams. Velocities of 
the current measured almost simultaneously at different points across the river, 
those measured in different sloughs of the upper part of Lake Keokuk, and those 
measured near the mouths of certain tributaries of the Mississippi, are given in 
Table 9. Most of the observations on the tributaries were made in September, 
when heavy showers caused a considerable rise of water in the Mississippi. The 
velocity of 4.38 feet per second in the Des Moines River was the greatest observed 
during the investigation. 
Table 9. — Variations in velocities of current measured at various points, Mississippi River, 1921. 
SIMULTANEOUSLY AT DIFFERENT POINTS ACROSS THE RIVER. 
Locality. 
Date. 
Velocity, 
feet per 
second. 
Locality. 
Date. 
Velocity, 
feet per 
second. 
Stations 4 and 5, New Boston, 111.: 
Main channel 
July 13 
2.8 
Stations 101 to 103, Reads Landing: 
Left shore 
Aug. 30 
0. 92 
Midstream 
2.5 
Midstream 
2.05 
3. 14 
Stations 96 to 98, above Lake Pepin: 
Left shore 
Right shore (main channel) 
Aug. 29 
.91 
Stations 104 to 106, above mouth of Chip- 
pewa River: 
Midstream (main channel) 
Right shore 
...do 
. . .do 
0 
Left shore.... 
0 
Midstream 
.77 
Right shore * 
. .do 
.77 
DIFFERENT SLOUGHS, UPPER PART OF LAKE KEOKUK. 
Stations 9, 10, 12, Dallas: 
Right channel ... 
Station 18, Turkey Chute 
July 21 
do 
0. 37 
July 15 
.do 
.8 
Station 19, Shokokon Slough 
1.0 
Left channel 
Chute 
.do 
1 8 
NEAR MOUTHS OF CERTAIN TRIBUTARIES. 
Stations 99 and 100, Chippewa River, 1 
mile above mouth: 
Left shore 
Aug. 30 
3.13 
Station 134, Root River 
Station 142, Wisconsin River 
Station 144, Turkey River 
Sept. 12 
Sept. 14 
1.23 
2.42 
1.83 
Right shore 
2.42 
Station 149, Rock River 
Sept. 18 
Sept. 20 
Sept. 23 
2.20 
Station 132, Black River above the rail- 
road bridge 
Sept. 12 
.34 i 
Station 152, Iowa River 
1 Station 158, Des Moines River 
3.14 
